1. Field of the Invention
The present invention relates to an image processing device and an image processing method, and more particularly to an image processing device and an image processing method that perform quantization to convert input image data into output image data while distributing error between input image data and output image data to image data of not-yet-processed peripheral pixels.
2. Description of Related Art
Recently, color printers, such as ink-jet printers, that have a print head for ejecting ink of a plurality of colors have become popular as computer output devices, and are widely used for executing multi-color and multi-tone printing of images processed by a computer or the like. The ink-jet printer reproduces tones corresponding to input tone data. (gray-scale data) by controlling the dot generation ratio in each area.
An error distribution method has been proposed to control dot generation on a pixel-by-pixel basis. This method controls dot formation to decrease the density error of an overall image by determining an error that occurs on a pixel due to mismatch between density represented by input tone data and density actually reproduced by the presence or absence of dot formation and by distributing the error to peripheral unprocessed pixels. Presence or absence of dot formation at each pixel is determined based on corrected tone data that is produced by distributing errors to the original input tone data of the subject pixel from already-processed peripheral pixels. With this error distribution method, the overall image error can be made extremely small, and output image quality can be improved.
Recently, there have been proposed ink-jet printers of a type that can reproduce three or more values per dot by varying the dot size, rather than reproducing two values by simply turning a dot on or off. A multi-value error distribution method has been proposed to handle three or more values.
According to the multi-value error distribution method, however, so-called false edges occur in parts of a gradation image where tones vary continuously.